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authorThomas Gleixner <tglx@linutronix.de>2019-11-18 14:28:24 +0100
committerThomas Gleixner <tglx@linutronix.de>2020-03-28 13:21:08 +0100
commitf1e67e355c2aafeddf1eac31335709236996d2fe (patch)
tree6405dfe9656d09114a8aec1c87cffe170fc6dec9
parentfc32150e6f43d6cb93ea75937bb6a88a1764cc37 (diff)
downloadlinux-f1e67e355c2aafeddf1eac31335709236996d2fe.tar.bz2
fs/buffer: Make BH_Uptodate_Lock bit_spin_lock a regular spinlock_t
Bit spinlocks are problematic if PREEMPT_RT is enabled, because they disable preemption, which is undesired for latency reasons and breaks when regular spinlocks are taken within the bit_spinlock locked region because regular spinlocks are converted to 'sleeping spinlocks' on RT. PREEMPT_RT replaced the bit spinlocks with regular spinlocks to avoid this problem. The replacement was done conditionaly at compile time, but Christoph requested to do an unconditional conversion. Jan suggested to move the spinlock into a existing padding hole which avoids a size increase of struct buffer_head on production kernels. As a benefit the lock gains lockdep coverage. [ bigeasy: Remove the wrapper and use always spinlock_t and move it into the padding hole ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Christoph Hellwig <hch@infradead.org> Link: https://lkml.kernel.org/r/20191118132824.rclhrbujqh4b4g4d@linutronix.de
-rw-r--r--fs/buffer.c19
-rw-r--r--fs/ext4/page-io.c8
-rw-r--r--fs/ntfs/aops.c9
-rw-r--r--include/linux/buffer_head.h6
4 files changed, 16 insertions, 26 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index b8d28370cfd7..6b3495827cad 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -274,8 +274,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
* decide that the page is now completely done.
*/
first = page_buffers(page);
- local_irq_save(flags);
- bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
+ spin_lock_irqsave(&first->b_uptodate_lock, flags);
clear_buffer_async_read(bh);
unlock_buffer(bh);
tmp = bh;
@@ -288,8 +287,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
}
tmp = tmp->b_this_page;
} while (tmp != bh);
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
/*
* If none of the buffers had errors and they are all
@@ -301,8 +299,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
return;
still_busy:
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
return;
}
@@ -371,8 +368,7 @@ void end_buffer_async_write(struct buffer_head *bh, int uptodate)
}
first = page_buffers(page);
- local_irq_save(flags);
- bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
+ spin_lock_irqsave(&first->b_uptodate_lock, flags);
clear_buffer_async_write(bh);
unlock_buffer(bh);
@@ -384,14 +380,12 @@ void end_buffer_async_write(struct buffer_head *bh, int uptodate)
}
tmp = tmp->b_this_page;
}
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
end_page_writeback(page);
return;
still_busy:
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
return;
}
EXPORT_SYMBOL(end_buffer_async_write);
@@ -3385,6 +3379,7 @@ struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
if (ret) {
INIT_LIST_HEAD(&ret->b_assoc_buffers);
+ spin_lock_init(&ret->b_uptodate_lock);
preempt_disable();
__this_cpu_inc(bh_accounting.nr);
recalc_bh_state();
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 68b39e75446a..de6fe969f773 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -125,11 +125,10 @@ static void ext4_finish_bio(struct bio *bio)
}
bh = head = page_buffers(page);
/*
- * We check all buffers in the page under BH_Uptodate_Lock
+ * We check all buffers in the page under b_uptodate_lock
* to avoid races with other end io clearing async_write flags
*/
- local_irq_save(flags);
- bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
+ spin_lock_irqsave(&head->b_uptodate_lock, flags);
do {
if (bh_offset(bh) < bio_start ||
bh_offset(bh) + bh->b_size > bio_end) {
@@ -141,8 +140,7 @@ static void ext4_finish_bio(struct bio *bio)
if (bio->bi_status)
buffer_io_error(bh);
} while ((bh = bh->b_this_page) != head);
- bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&head->b_uptodate_lock, flags);
if (!under_io) {
fscrypt_free_bounce_page(bounce_page);
end_page_writeback(page);
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 7202a1e39d70..554b744f41bf 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -92,8 +92,7 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
"0x%llx.", (unsigned long long)bh->b_blocknr);
}
first = page_buffers(page);
- local_irq_save(flags);
- bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
+ spin_lock_irqsave(&first->b_uptodate_lock, flags);
clear_buffer_async_read(bh);
unlock_buffer(bh);
tmp = bh;
@@ -108,8 +107,7 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
}
tmp = tmp->b_this_page;
} while (tmp != bh);
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
/*
* If none of the buffers had errors then we can set the page uptodate,
* but we first have to perform the post read mst fixups, if the
@@ -142,8 +140,7 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
unlock_page(page);
return;
still_busy:
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
return;
}
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 7b73ef7f902d..e0b020eaf32e 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -22,9 +22,6 @@ enum bh_state_bits {
BH_Dirty, /* Is dirty */
BH_Lock, /* Is locked */
BH_Req, /* Has been submitted for I/O */
- BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise
- * IO completion of other buffers in the page
- */
BH_Mapped, /* Has a disk mapping */
BH_New, /* Disk mapping was newly created by get_block */
@@ -76,6 +73,9 @@ struct buffer_head {
struct address_space *b_assoc_map; /* mapping this buffer is
associated with */
atomic_t b_count; /* users using this buffer_head */
+ spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to
+ * serialise IO completion of other
+ * buffers in the page */
};
/*